The present invention relates generally to methods and apparatuses for adding solid alloying ingredients to molten metal and more particularly to the addition of solid, particulate alloying ingredients to a stream of molten metal descending from an upper container to a lower container.
It is oftentimes desirable to add alloying ingredients, in solid, particulate form, to a molten metal stream descending from an upper container, such as a ladle, to a lower container, such as the tundish of a continuous casting apparatus. Certain alloying ingredients, such as lead, bismuth, tellurium and selenium, typically added to steel to improve the machinability thereof, have relatively low melting points compared to steel and are prone to excessive fuming when added to molten steel.
One procedure heretofore contemplated for adding these alloying ingredients to molten steel comprises injecting solid particles of these ingredients into a descending stream of molten metal contained within and completely filling the cross-section of an elongated conduit extending between and communicating with both the ladle and the tundish. The solid particles are mixed with a transport gas, and the mixture is introduced into the descending stream of molten metal through an injection port in the conduit. However, a number of problems can arise should this procedure be employed. For example, the molten metal can back up through the injection port, there can be a pulsing delivery of the solid particles rather than a uniform delivery thereof and there can be a plugging of the injection nozzle.